Virtual reality system locomotion interface utilizing a pressure-sensing mat

ABSTRACT

A virtual reality system transposes a user&#39;s position and movement in real space to virtual space. The virtual reality system includes a locomotion interface that outputs signals indicative of a user&#39;s position in real space. The locomotion interface includes a pressure-sensing mat having a base layer, a plurality of pressure sensing elements and a counter-force generating layer formed over the base layer, and a top layer formed over the plurality of pressure-sensing elements. The plurality of pressure sensing elements output a signal indicative of pressure applied to the top layer. A virtual reality processor uses the signals output by the locomotion interface to produce an output indicative of the user&#39;s position in the virtual space corresponding to the user&#39;s position and movement in the real space. A display uses the output from the virtual reality processor to produce an image of the virtual space.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] This invention relates to virtual reality systems that can beused to fully immerse a user in virtual space.

[0003] 2. Description of Related Art

[0004] Virtual reality is a computer-generated environment in which auser is immersed. Actions of the user are translated by a computer intoinputs that effect the virtual environment (VE). Virtual reality systemsmay stimulate naturally occurring senses, such as sight, sound, touchand movement, so that a user can navigate through a virtual environmentas if in the real world.

[0005] A major challenge to virtual reality system designers is todesign a virtual reality system that allows natural human locomotion.Previous virtual reality systems that allow the user to move naturallyrequire complex and expensive equipment. Other virtual reality systemsabandon the concept of natural human locomotion, using simple hardwarethat allow the user to navigate through the virtual environment withartificial gestures, such as flying in the virtual space in thedirection the user's finger is pointing.

[0006] Known virtual reality systems include treadmill devices thattrack the user's movement on the treadmill. Such a device is disclosedin U.S. Pat. No. 5,562,572 to Carmein. Although these treadmill devicesallow movement in the user's upright position, they do not allowmovement in the user's prone position. They also cannot sense whetherthe user is in the standing, crawling or prone position. Further, thesetreadmill devices are often mechanically complicated, and are thusencumbered by the inherent lag times and momentum problems associatedwith moving mechanical masses.

[0007] Other known virtual reality systems allow the user to move in theprone position, but sacrifice natural motion. For example, one knowndevice includes a simple foot-pedal interface, similar to theaccelerator of an automobile. The foot-pedal allows the user to moveforward or backward, depending on where the user presses the foot-pedal.In this system, the user always moves toward the center of the field ofview, and the field of view is rotated if the user turns his head past acertain angle. Although this system allows a user to navigate from anyposture, the user must be in constant contact with the foot-pedal tonavigate. It also does not enable the user to move naturally.

SUMMARY OF THE INVENTION

[0008] In various exemplary embodiments, the virtual reality systemaccording to one aspect of this invention includes a pressure-sensingmat that outputs signals indicative of a user's position in real space.A virtual reality processor uses the signals output by thepressure-sensing mat to produce an output indicative of the virtualspace corresponding to the user's position and movement in real space. Adisplay device uses the output from the virtual reality processor toallow the user to be fully immersed in the virtual space.

[0009] In various exemplary embodiments, the pressure sensing matincludes a base layer, a plurality of pressure sensing elements formedover the base layer, and a top layer formed over the plurality ofpressure-sensing elements. The plurality of pressure sensing elementsoutput a signal indicative of pressure applied to the top layer.

[0010] This invention provides a virtual reality system that has asimple design and that allows a user to move naturally in any directionfrom any posture (e.g., standing, crawling, prone). The virtual realitysystem according to this invention has many advantages over previousvirtual reality systems. The enhanced flexibility of the variousexemplary embodiments of the system according to this invention allows auser to move forward, backward, or sideways from a prone, crawling orstanding position. Thus, the virtual reality system according to thisinvention has many applications, such as, for example, enhanced militarytraining, realistic video game environments, and a broad range ofmedical and therapeutic applications.

[0011] These and other features and advantages of this invention aredescribed in, or are apparent from, the following detailed descriptionof various exemplary embodiments of the systems and methods according tothis invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various exemplary embodiments of this invention will be describedin detail, with reference to the following figures, wherein:

[0013]FIG. 1 illustrates one exemplary embodiment of a virtual realitysystem according to this invention;

[0014]FIG. 2 illustrates one exemplary embodiment of the pressuresensing mat according to this invention;

[0015]FIG. 3 shows one exemplary embodiment of a pressure sensitiveresistor usable with the various exemplary embodiments of the virtualreality system according to this invention;

[0016]FIG. 4 illustrates the equivalent circuit of the pressure sensingmat according to this invention;

[0017]FIG. 5 shows another exemplary embodiment of the pressure sensingmat according to this invention; and

[0018]FIG. 6 is a block diagram of an exemplary embodiment of thevirtual reality processor according to this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0019]FIG. 1 illustrates one exemplary embodiment of a virtual realitysystem according to this invention. The virtual reality system 1includes a pressure sensing mat 100, a virtual reality (VR) processor200, and a display 400. It should be appreciated that the variousexemplary embodiments of the virtual reality system according to thisinvention can have any number and configuration of components that use apressure sensing mat to sense the user's movement in order to generate avirtual environment.

[0020]FIG. 2 illustrates one exemplary embodiment of the pressuresensing mat 100 according to this invention. The pressure sensing mat100 includes a semi-rigid base layer 120. Any suitable material can beused for the base layer 120, such as, for example, plastic, hardwood,and polycarbonate (lexan). A grid 140 (i.e., a two-dimensional array) ofpressure sensing elements 150-1 to 150-n is formed over the base layer120. A top layer 160 is formed over the grid 140. Any suitable layer canbe used for the top layer 160, such as, for example, rubber, naturalrubber, buna's rubber, and fabric reinforced negro rubber, is preferred.

[0021] The pressure sensing elements 150-1 to 150-n of the grid 140detect the pressure applied to fixed points on the top layer 160 of thepressure sensing mat 100. Any suitable pressure sensing device can beused for the pressure sensing elements 150-1 to 150-n, such as, forexample, electromechanical pressure sensors. In general, any known orlater discovered pressure sensing device can be used for the pressuresensing elements 150-1 to 150-n.

[0022] In the exemplary embodiment shown in FIG. 1, the pressure sensingelements 150-1 to 150-n include force sensitive resistors. As is knownin the art, force sensitive resistors include elements that act assimple voltage dividers. FIG. 3 shows one exemplary embodiment of apressure sensitive resistor 180 usable with the various exemplaryembodiments of the virtual reality system according to this invention.The pressure sensing elements 150-1 to 150-n include correspondingpressure sensitive resistors 180-1 to 180-n. Each pressure sensitiveresistor 180 includes an upper film 181, a lower film 182, a firstelectrode pattern 183 formed over the lower film 182, a second electrodepattern 184 formed over the upper film 181 so as to oppose the electrodepattern 183, and a pressure-sensitive conductor 185 formed over thesecond electrode pattern 184. When the upper film 181 is pressed, thepressure sensitive conductor 185 is compressed between the first andsecond electrode patterns. As is known in the art, the resistance of thepressure sensitive conductor 185 is lowered when compressed.Accordingly, voltage output of the pressure sensitive resistor 180 willvary with applied pressure. For more details of a pressure-sensitiveresistor, see U.S. Pat. No. 5,948,990, the disclosure of which isincorporated herein by reference.

[0023]FIG. 4 illustrates the equivalent circuit of the pressure sensingmat 100. The voltage outputs Vout-1 to Vout-n correspond to respectivepressure sensing elements 150-1 to 150-n that make up the grid 140. Auser applies pressure to points on the pressure sensing mat 100 as theuser navigates through the virtual reality environment. The appliedpressures alter the resistance of the pressure sensitive resistors 180-1to 180-n, and thus the voltage output of each of the correspondingpressure sensing elements 150-1 to 150-n varies as the user moves. Thegrid 140 produces a voltage output that can be analyzed to generate apattern that shadows the user's movements in the virtual space.

[0024]FIG. 5 illustrates another exemplary embodiment of the pressuresensing mat 100 according to this invention. In this embodiment, thepressure sensing mat 100 includes the same elements as in the firstembodiment, i.e., a semi-rigid base layer 120, a grid 140 of pressuresensing elements 150-1 to 150-n, and a top layer 160, and also includesa counter force generating layer 190. Although FIG. 5 shows the counterforce generating layer 190 disposed between the grid 140 and the toplayer 160, it should be appreciated that the counter force generatinglayer 190 can be disposed between any two layers of the pressure sensingmat 100 or at the top or bottom surface of the pressure sensing mat 100.The counter force generating layer 190 can be made up of a grid ofcounter force generating elements 195-1 to 195-n. Any suitable counterforce generating device can be used for the counter force generatingelements 195-1 to 195-n, such as, for example, springs, hydraulicdevices, pneumatic devices, or electromechanical devices.

[0025] In operation, the voltage output of each of the pressure sensingelements 150-1 to 150-n can be used to activate a corresponding one orgroup of counter force generating elements 195-1 to 195-n. The counterforce generating elements 195-1 to 195-n can provide a counter force tothe user's body as the user moves over the pressure sensing mat 100. Aswill be discussed in further detail, the counter-force generated by thecounter force generating elements 195-1 to 195-n can vary based on thetype of virtual ground surface generated by the virtual reality system1.

[0026]FIG. 6 is a block diagram of an exemplary embodiment of thevirtual reality processor 200. The virtual reality processor includes acontroller 210, a memory 220 (including RAM and ROM, for example), apattern generation device 230, a motion identification device 240, avirtual environment rendering device 250, an input interface 260, and anoutput interface 270. The controller 210 interfaces with the othercomponents 220-270 using a control/data bus 280. Although the exemplaryvirtual reality processor 200 uses a bussed architecture, it should beappreciated that the exemplary virtual reality processor 200 can use anyknown or later developed architectures, including ASIC, a programmedgeneral purpose computer, discrete logic devices, etc.

[0027] Under control of the controller 210, the input interface 260 canreceive analog voltage signals from the pressure sensing elements 150-1to 150-n. The input interface 260 can include an analog to digitalconverter that converts the analog voltage signals to digital signals.The input interface 260 can input the digital signals to the memory 220for storage.

[0028] Next, the controller 210 can provide the digital signals storedin the memory 220 to the pattern generation device 230. The patterngeneration device 230 samples the digital signals stored in the memory220 at regular intervals and generates a pattern based on the digitalsignals at the regular intervals. The patterns generated by the patterngeneration device 230 represent various positions of the user on thepressure sensing mat 100.

[0029] The controller 210 transfers the patterns generated by thepattern generation device 230 to the motion identification device 240.The motion identification device 240 can include a pattern recognitiondevice (not shown) that identifies a given pattern with a correspondingposition of the user. The pattern recognition device can identify apattern by comparing the pattern with a database of patterns stored inthe memory 220. The pattern recognition device can also recognize thepattern based on the size, shape and/or pressure distribution of thepattern. For example, if the pattern is larger than a predeterminedthreshold size, the pattern recognition device will recognize thepattern as a “prone user position” pattern. Similarly, if the matoutputs signals indicative of two patterns of a similar size thatalternately move, the processor determines that the user is upright(e.g., walking, running or standing (if the two patterns do not move)).If more than two smaller moving patterns are detected, the user isdetermined to be crawling. The patterns stored in the memory 220 canprovide examples for a neural network to learn how to identify differentpatterns.

[0030] Based on the posture and directional information determined bythe processor, the virtual environment (i.e., the displaying image) isappropriately altered.

[0031] A series of user positions identified by the pattern recognitiondevice can be stored in the memory 220 during fixed intervals as theuser navigates through the virtual environment. Preferably, the centroidof each of the patterns in the series of patterns is tracked as the usermoves on the pressure sensing mat 100. The motion identification device240 can sample the series of user positions at the end of the fixedintervals and identify the motion of the user during the fixed intervalsbased on the series of user positions. The motion includes, for example,direction (forward, backward, left, right, etc.) and speed. The patternsalso can be analyzed to determine the posture (standing, crawling,prone) of the user.

[0032] The direction that the user is facing is determined by a sensorthat can be directly attached to the user. In embodiments, the sensorcan be a magnetic tracker attached to the user's waist that determinesthe direction the waist is facing. The virtual reality system accordingto this invention provides significant advantages over known virtualreality systems in that only a single sensor needs to be directlyattached to the user. Thus, the user is relatively free from cumbersomesensor wiring and devices.

[0033] The controller 210 can transpose the motion of the user into thevirtual environment generated by the virtual environment renderingdevice 250. Data for the virtual environment, including virtual objects,can be stored in the memory 220. The virtual environment renderingdevice 250 can update the virtual environment at given intervals basedon the data stored in the memory 220. The virtual environment renderingdevice 250 can update the virtual space each time the user's motion isidentified. Thus, as the user moves through the virtual space, the usercan effect, and can be effected by, the virtual environment. Forexample, as the user navigates through the virtual space, the user'sperspective in the virtual space can change, virtual objects can enterthe user's path, and the user can move virtual objects.

[0034] The virtual environment rendering device 250 can also generate avirtual ground surface, depending on the user's location in the virtualspace. The type of virtual ground surface generated by the virtualenvironment rendering device 250 can determine the amount of counterforce generated by the counter force generating layer 190 of thepressure sensing mat 100. For example, if the virtual ground surface issoft grass, the counter force generating layer 190 can be controlled toexert a spring-like counter force to the user's foot.

[0035] The controller 210 can control the output interface 270 to outputvirtual reality environment data to the display 400. Although thedisplay 400 is shown in FIG. 1 as a head-mounted display, any known orlater discovered display can be used. Preferably, the display providesthe user with the ability to see, hear, smell and/or touch in thevirtual world so that the user is fully immersed in the virtual space.

[0036] In embodiments, it is conceivable that the pressure sensing mat100 can be as large as required to allow the user to move as if the userwas in the virtual space. For example, the pressure sensing mat 100 canbe made to cover the floor of a large field or room. Alternatively, ifspace is limited, the pressure sensing mat 100 can be made smaller, inwhich case the user would be required to move in a bounded area or move“in place”.

[0037] The virtual reality system 1 can be implemented as softwareexecuting on a programmed general purpose computer, a special purposecomputer, a microprocessor or the like.

[0038] While the invention has been described with reference toexemplary embodiments thereof, it is to be understood that the inventionis not limited to the preferred, exemplary embodiments or constructions.To the contrary, the invention is intended to cover variousmodifications and equivalent arrangements. In addition, while thevarious elements of the exemplary embodiments are shown in variouscombinations and configurations, which are exemplary, other combinationsand configurations, including more, less or only a single element, arealso within the spirit and scope of the invention.

What is claimed is:
 1. A locomotion interface that provides inputsignals, indicative of a user's movement, to a virtual reality system,the locomotion interface comprising: a pressure-sensing mat including abase layer, a plurality of pressure sensing elements and a counter-forcegenerating layer formed over the base layer, and a top layer formed overthe plurality of pressure-sensing elements, wherein the plurality ofpressure sensing elements output signals indicative of pressure appliedto the top layer.
 2. The locomotion interface of claims 1, wherein thecounter-force generating layer is made up of a plurality ofcounter-force generating elements.
 3. The locomotion interface of claim2, wherein the plurality of counter-force generating elements make up agrid.
 4. The locomotion interface of claim 2, wherein the counter-forcegenerating elements are at least one of springs, hydraulic devices,pneumatic devices and electromechanical devices.
 5. The locomotioninterface of claim 1, wherein the plurality of pressure-sensing elementsmake up a grid.
 6. The locomotion interface of claim 1, wherein theplurality of pressure-sensing elements comprise force sensitiveresistors.
 7. The locomotion interface of claim 1, wherein the baselayer comprises a semi-rigid material.
 8. The locomotion interface ofclaim 1, wherein the base layer comprises plastic.
 9. The locomotioninterface of claim 1, wherein the top layer comprises rubber.
 10. Avirtual reality system comprising the locomotion interface of claim 1.11. A virtual reality system that transposes a user's position andmovement in real space to virtual space, the virtual reality systemcomprising: a locomotion interface that outputs signals indicative of auser's position in real space, the locomotion interface including apressure-sensing mat including a base layer, a plurality of pressuresensing elements and a counter-force generating layer formed over thebase layer, and a top layer formed over the plurality ofpressure-sensing elements, the plurality of pressure sensing elementsoutput signals indicative of pressure applied to the top layer; avirtual reality processor that uses the signals output by the locomotioninterface to produce an output indicative of the user's position in thevirtual space corresponding to the user's position and movement in thereal space; and a display that uses the output from the virtual realityprocessor to produce an image of the virtual space.
 12. The locomotioninterface of claims 11, wherein the counter-force generating layer ismade up of a plurality of counter-force generating elements.
 13. Thelocomotion interface of claim 12, wherein the plurality of counter-forcegenerating elements make up a grid.
 14. The locomotion interface ofclaim 12, wherein the counter-force generating elements are at least oneof springs, hydraulic devices, pneumatic devices and electromechanicaldevices.
 15. The virtual reality system of claim 11, wherein the displayis a head mounted display.
 16. The virtual reality system of claim 11,wherein the plurality of pressure-sensing elements make up a grid. 17.The virtual reality system of claim 11, wherein the plurality ofpressure-sensing elements comprise force sensitive resistors.
 18. Thevirtual reality system of claim 11, wherein the base layer comprises asemi-rigid material.
 19. The virtual reality system of claim 11, whereinthe base layer comprises plastic.
 20. The virtual reality system ofclaim 11, wherein the top layer comprises rubber.
 21. The virtualreality system of claim 11, wherein the virtual reality processorcomprises: a pattern generator that uses the signals output from thelocomotion interface to generate a plurality of corresponding patterns;a motion identifier that uses the plurality of patterns generated by thepattern generator to identify a corresponding plurality of userpositions and user movements; and a virtual environment renderer thatuses the identified user positions and movements to generate a virtualspace such that the user can effect, and be effected by, the virtualspace.
 22. The virtual reality system of claim 21, wherein the virtualspace generated by the virtual environment renderer includes a virtualground surface.
 23. The virtual reality system of claim 22, wherein thevirtual ground surface generated by the virtual environment rendererdetermines the amount of counter-force generated by the counter-forcegenerating layer.
 24. The virtual reality system of claim 21, whereinthe plurality of positions identified by the motion identifier compriseat least one of a prone user position, a crawling user position, and astanding user position.
 25. The virtual reality system of claim 21,wherein the plurality of motions identified by the motion identifiercomprise at least one of a backward user motion, a sideways user motion,a forward user motion, and a diagonal user motion.
 26. A method ofproviding input signals, indicative of a user's movement, to a virtualreality system, comprising: sensing pressure applied to a locomotioninterface having a pressure-sensing mat including a base layer, aplurality of pressure sensing elements and a force-generating layerformed over the base layer, and a top layer formed over the plurality ofpressure-sensing elements.
 27. The method of claim 26, furthercomprising: processing signals output by the locomotion interface, inresponse to the sensed pressure, to produce an input signal indicativeof the user's position in virtual space corresponding to the user'sposition and movement in real space.
 28. The method of claim 26, whereinthe step of processing the signals output by the locomotion interfacecomprises: generating a plurality of patterns that correspond to thesignals output by the locomotion interface; and identifying a pluralityof user positions and user movements that correspond to the plurality ofpatterns.